1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a folder for a printing press.
2. Background of the Invention
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web is cut into signatures and then folded. Various types of folders are known in the art, one of which is a combination folder.
Generally, combination folders incorporate a series of cylinders that uniquely provide functions to complete different portions of the fold, with each cylinder able to perform one or more functions. In order to provide for different types of printed products, the relative positions of cylinders within the combination folder may be altered. FIG. 1 shows the basic cylinder construction for a combination folder, for example a tucking cylinder. The basic cylinder shown herein is known in the art and is provided here for improved understanding of the present invention. A first function part 1, such as a tucking section, is mounted directly to a shaft 2 of the cylinder by a first arm 3 and a second arm 4. The shaft 2 supports a first hollow hub 5 and second hollow hub 6, which run concentric to the shaft 2. First and second hollow hubs 5, 6, in turn, support a third arm 8 and a fourth arm 9, which support a second function part 7, for example a gripper section. The shaft 2 and each hub 5, 6 can be driven by first and second drive gears 10, 11, respectively, which can be phased with respect to each other using helical gears.
Existing combination folders typically require a fold mode change and incorporate air cylinders to slide the helical gears to a required position. The helical gears, which are keyed to the main cylinder bodies, in turn, phase the cylinder bodies. This is incorporated to phase one set of cylinder bodies with respect to the other.
A drawback of the air cylinder and helical gear structure is that the helical gears may fail to shift, or seize, when changing relative position. This is due to the weight of the cylinder bodies or from the hubs freezing to the shaft due to lack of lubricant or due to fretting corrosion.
In order to reduce the likelihood of seizing, periodic maintenance is performed on the combination folder. However, the maintenance is time-consuming and increases the downtime of the folder.
U.S. Pat. No. 5,405,126 purports to disclose a folder having at least a first longitudinal folding device, driven severing members, and a second longitudinal folding device to which folding copies are supplied via a section of a conveyor belt which is disposed over a second loadable copy delivery. The folder comprises drawing devices disposed upstream of the severing members in the web-and-copy direction, first drive means for separately and controllably driving said drawing devices, and second drive means for driving said severing members and said cross-folding devices. The folder further includes a separate drive for driving said outwardly swingable conveyor belts. The second longitudinal folding device comprises components, and may include a phase-controllable separate electric motor for driving said components. The second drive means is an electric-motor drive. From one of the cutting or severing cylinders, the drive of the electric motor is transmitted to a gear. By means of the gear, the drive drives a folding cylinder, from there to a folding-jaw cylinder and then to a gripper cylinder. Furthermore, the drive of the second longitudinal fold can also be effected by the electric motor.
The '126 patent has the disadvantage that the folding cylinder, folding-jaw cylinder, and gripper cylinder are driven by the same drive and, thus, adjustment and mode changes are difficult.
European Patent Application No. 0 699 524 A2 purports to disclose a printing unit with elements driven by dependent electric motors, identified by the letter M in the figures. Folding devices in figure twenty-two each have a separate motor that directly drives the folding cylinders in the folding devices. EP Patent No. EP 0 699 524 A2 has the disadvantage that one motor drives the folding cylinders of a folder, thus making phase changes difficult.